SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68b037f32885574437bc50b910af1f3545bcec0b3d214f456ec4e9579dca0894' 
  AND token = 'wyWl9vZcHCVLCUSXPoMYvn46s89LPQP3fgk2n9bmk40=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}